peer-impl.go    |  3 +--
 peerconn.go     | 18 +++++++++---------
 webseed-peer.go |  3 +--

diff --git a/peer-impl.go b/peer-impl.go
index f7140377388125fb073a3ae3a55359855b7ae8a6..d400d9a4c9790b9b35d72234bf19bf0e5c7adfd2 100644
--- a/peer-impl.go
+++ b/peer-impl.go
@@ -17,9 +17,8 @@ 	writeInterested(interested bool) bool
 
 	// Neither of these return buffer room anymore, because they're currently both posted. There's
 	// also PeerConn.writeBufferFull for when/where it matters.
-	_cancel(RequestIndex) bool
+	_cancel(RequestIndex)
 	_request(Request) bool
-
 	connectionFlags() string
 	onClose()
 	onGotInfo(*metainfo.Info)
diff --git a/peerconn.go b/peerconn.go
index 0eec60370bfc2713a8644af2a067f75db47cb032..4f43d50d3e444e9c61d67000947abf106e039c5a 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -638,17 +638,17 @@ 		Length: r.Length,
 	})
 }
 
-func (me *Peer) cancel(r RequestIndex) bool {
+func (me *Peer) cancel(r RequestIndex) {
 	if !me.actualRequestState.Requests.Contains(r) {
-		return true
+		panic(r)
 	}
-	return me._cancel(r)
+	me._cancel(r)
 }
 
-func (me *PeerConn) _cancel(r RequestIndex) bool {
+func (me *PeerConn) _cancel(r RequestIndex) {
 	if me.cancelledRequests.Contains(r) {
 		// Already cancelled and waiting for a response.
-		return true
+		panic(r)
 	}
 	// Transmission does not send rejects for received cancels. See
 	// https://github.com/transmission/transmission/pull/2275.
@@ -662,7 +662,7 @@ 		if me.isLowOnRequests() {
 			me.updateRequests("Peer.cancel")
 		}
 	}
-	return me.write(makeCancelMessage(me.t.requestIndexToRequest(r)))
+	me.write(makeCancelMessage(me.t.requestIndexToRequest(r)))
 }
 
 func (cn *PeerConn) fillWriteBuffer() {
@@ -1395,12 +1395,12 @@ 	// waiting for it to be written to storage.
 	piece.unpendChunkIndex(chunkIndexFromChunkSpec(ppReq.ChunkSpec, t.chunkSize))
 
 	// Cancel pending requests for this chunk from *other* peers.
-	t.iterPeers(func(p *Peer) {
+	if p := t.pendingRequests[req]; p != nil {
 		if p == c {
-			return
+			panic("should not be pending request from conn that just received it")
 		}
 		p.cancel(req)
-	})
+	}
 
 	err := func() error {
 		cl.unlock()
diff --git a/webseed-peer.go b/webseed-peer.go
index 85e121194d28c22c6d3180a6d8a45cd79d7a1c80..0cf6c7daa364e560db79a5ddb65da2d35f6ec7c7 100644
--- a/webseed-peer.go
+++ b/webseed-peer.go
@@ -48,7 +48,7 @@ func (ws *webseedPeer) writeInterested(interested bool) bool {
 	return true
 }
 
-func (ws *webseedPeer) _cancel(r RequestIndex) bool {
+func (ws *webseedPeer) _cancel(r RequestIndex) {
 	active, ok := ws.activeRequests[ws.peer.t.requestIndexToRequest(r)]
 	if ok {
 		active.Cancel()
@@ -59,7 +59,6 @@ 	}
 	if ws.peer.isLowOnRequests() {
 		ws.peer.updateRequests("webseedPeer._cancel")
 	}
-	return true
 }
 
 func (ws *webseedPeer) intoSpec(r Request) webseed.RequestSpec {